cannot delete posts

Dear all…

I have installed my new blog and changed themes, add plugins etc and it’s all great…but I have realised that I cannot delete any posts from my manage->posts menue …the ‘delete’ button getting all a red background when I move my mouse over and the link is not active when I click …

I just cannot figure out where I have changed anything so severe that this simple task cannot be performed.

Any help is highly appreciated !
Thanks
Thomas